javac: add -d and multiple files examples

pages/common/javac.md

@@ -5,3 +5,15 @@
 - Compile a .java file:
 
 `javac {{filename.java}}`
+
+- Compile several .java files:
+
+`javac {{filename1.java}} {{filename2.java}} {{filename3.java}}`
+
+- Compile all .java files in current directory:
+
+`javac {{*.java}}`
+
+- Compile a .java file and place the resulting class file in a specific directory:
+
+`javac -d {{path/to/some/directory}} {{filename.java}}`